This invention relates to a field of medicine, in particular to diagnostic instruments, and more precisely to devices for mounting histological and biological specimens in an optical medium for subsequent microscopic examination.
The prepared and stained histological and biological specimens are placed in special mounting media to create an optically homogeneous medium and to ensure that the specimens will remain intact for the duration of the examination. The mounting media used include Cedar oil, cedax or polystyrene, for example.
Specimens are often mounted manually. To do this, the specimen is placed on a object slide, a drop of a xylene solution of the above mentioned medium is added and a cover glass is carefully positioned on the specimen. (Roskin G. I., Microscopic Technique, “Sovetskaya Nauka” State Publishing House, Moscow 1951, p. 152; Merkulov G. A., A Brief Introduction to Pathohistological Technique, “Medgis”, Leningrad 1951, p. 86; Romeis B., Microscopic Technique, “IL”, Moscow 1953, pp. 191-192.) Another method consists of placing a drop of a resin dissolved in xylene on an appropriately sized cover glass and then carefully lowering the object slide with the specimen on it until the specimen makes contact with the drop of solution on the cover glass (Lilli R., Technique of Pathology and Practical Histochemistry, “Mir”, Moscow 1969, p. 85).
It is mentioned in all sources that manually applying cover glasses may cause air bubbles to form beneath the cover glass which distort the microscopic image. These bubbles can be removed by carefully applying pressure to the cover glass with the tip of a dissecting needle. B. Romeis, however, points out that “the specimen is usually damaged” by such a procedure. Moreover, manually applying cover glasses is labor- and time-consuming, hardly efficient and can only be performed by trained personnel with appropriate experience.
The Consul Automatic Coverslipper manufactured by the English company Shandon Life Sciences International Ltd. (Shandon Consul Automatic Coverslipper) is already known. It comprises a cover glass magazine with a pusher, a object slide holder, a mounting medium dispenser and a roller device.
The object slide slide holder consists of a plurality of semi-frames that are attached to a bar and are mounted so as to pivot perpendicularly thereto. In its initial position, the roller device of the Consul Automatic Coverslipper consists of a table and two rollers that are located beneath the cover glass. The table together with the rollers is adapted to be moved perpendicular to the surface of the cover glass. The rollers may be diverted by spring-biased connecting rods.
The object slides are placed on the bar which is adapted to be moved vertically. The object slides are then supplied to the work area with the help of a pivoting device. The object slide magazine and the dispenser are mounted on the frame.
The Consul Automatic Coverslipper operates as follows.
The object slide pusher moves along guideways, thus transporting the lowermost cover glass from the magazine to the work area. One dose of the mounting medium is dropped onto the cover glass from above. The pivoting device pivots the semi-frame together with the object slide into the work area and positions the object slide above the cover glass with the specimen being located on the underside. The table of the roller unit rises, thus bringing the cover glass into approximation with the object slide. The pusher of the roller unit raises the rollers until these make contact with the cover glass, whereupon the spring-biased connecting rods begin to diverge and the rollers roll over the surface of the cover glass. Hence, the center portion of the cover glass is pressed by the table, whereas the side portions are rolled by the rollers. The roller unit eventually lowers and disengages the cover glass, while the pivoting device moves the semi-frames with the mounted object slide into the initial position.
The Consul Automatic Coverslipper is capable of mounting as many as 400 specimens per hour. By virtue of this high output, it can be used successfully in pathohistological laboratories.
The disadvantages of the Consul Automatic Coverslipper are that cover glass and object slide are held horizontally during pressing and this makes it difficult to remove air bubbles from the mounting medium.
A coverslipping device is also known according to U.S. Pat. No. 4,428,793, IPK B65C 9/08, published on Jan. 31, 1984, which comprises a cover glass magazine, a table for receiving the object slide and a device for removing the cover glass from the magazine, transporting it to the object slide table and applying it to the object slide. This device consists of a holder provided with a suction cup and a spring-loaded pusher, the suction cup being located above the pusher. The holder is lowered into the cover glass magazine until the suction cup engages a cover glass. The spring of the pusher is compressed until the pusher is level with the suction cup. Once the cover glass has been removed from the magazine, the pusher spring expands and pushes one end of the cover glass downwards. While it is being transported to the object slide table, the cover glass is slightly inclined owing to the difference in the levels of the suction cup and the pusher. The holder lowers the cover glass with its lower end onto the edge of the object slide at which a drop or smear of the mounting medium is located. While the cover glass is being lowered, the pusher presses against it. The pusher spring is compressed until the suction and pusher are horizontal—only then is the suction cup disengaged from the cover glass. Hence, the cover glass is first placed on the object slide gradually and at a specific angle, thereby allowing air bubbles to be eliminated from the medium more easily.
The disadvantage of this device is that it is difficult to remove an individual cover glass with a thickness of maximum 0.06-0.25 mm from the stack in the cover glass magazine, all the more so since the spring force of the pusher acts on the cover glass stack every time a cover glass is removed. In addition, when applying the cover glass, the force required to compress the spring may cause the specimen to be damaged.
The device for removing and applying cover glasses in accordance with U.S. Pat. No. 5,989,386, IPK B32 B31/04, published on Nov. 23, 1999, comprises an application head, at one end of which there are located two suction cups at an angle to one another. Interposed between the suction cups is a spring-biased plunger capable of upward and downward movement that is driven by a solenoid. The plunger, when retracted, does not contact the cover glass. In addition, a spring-biased level is mounted at the other end of the application head opposite the suction cups and plunger.
This device operates as follows. The head is lowered into the cover glass magazine until the plunger contacts the uppermost cover glass, whereupon this is engaged by the suction cups. Owing to the spring action of the plunger and the angular positioning of the suction cups, the cover glass is bent and thus removed from the stack. The head then transports the cover glass to the object slide. The end of the cover glass located opposite the point of suction is now pushed downwards by the lever so that the cover glass is laid on the object slide at a specific angle relative to the horizontal. The head continues to move downwards until the end of the cover glass held by the suction cups rests against the object slide. The lever mounted on the application head—it is capable of moving clockwise and counterclockwise—then places the cover glass on the object slide, whereupon the suction cups are released.
The apparatus described in U.S. Pat. No. 5,989,386 is supposed to remove “a large percentage of individual cover glasses”. In practice, however, the apparatus is not always successful in removing an individual cover glass by means of the suction cups. Consequently, the cover glass must be ejected from the magazine by other devices before they can be successfully engaged by the suction cups. The use of a spring-biased plunger in addition to a lever may also cause damage to the specimen, exactly as in the case of the device according to U.S. Pat. No. 4,428,793.
The apparatus for mounting histological specimens in accordance with U.S. Pat. No. 6,474,386, IPK B65H29/24, published on Nov. 5, 2002, makes it possible to reliably remove the air from the space between the cover glass and object slide. This apparatus contains a platform for the object slide as well as a means for picking up a cover glass by suction and positioning it on the object slide in an angular fashion. This suction and positioning means comprises a cylinder mounted on a stand next to the platform and capable of upward and downward movement by means of a motor. This cylinder also has mounted on it a holder arm provided with its own motor and capable of clockwise and counterclockwise rotation. The free end of the holder arm has a suction cup connected to a vacuum pump. The holder arm can raise and lower the suction cup until the cover glass to be transported is located in a horizontal position.
The apparatus according to U.S. Pat. No. 6,474,386 operates as follows.
A object slide with a specimen and a drop of mounting medium is placed on the platform. The suction means picks up the cover glass with the help of the suction cup at one end and positions it above the object slide such that the engaged end is higher than the free end. The cylinder now moves downwards until the horizontal axis of the holder arm mount is located below the object slide on the platform. In this position, the lower end of the cover glass contacts the edge of the object slide at an acute angle to the horizontal. The motor-driven holder arm now rotates counterclockwise, whereupon the cover glass held by the suction cup is gradually lowered onto the object slide. The suction cup is then disengaged. It is claimed that the apparatus is capable of mounting histological specimens without damage.
The drawback of the cited apparatus lies in how the cover glass is picked up by means of the suction cup. This construction requires a vacuum pump as well as a complicated control unit, thus increasing both the weight of the apparatus as well as the cost of manufacturing it.